The subject invention is method of producing a plastic article utilizing a lost core process, and specifically a method of producing a plastic article by supporting inserts within a lost core assembly for positioning within the completed plastic article.
Conventional lost core-molding processes include the formation of a core defining a desired inner cavity configuration of the completed part. The core is formed from an alloy having a low melting temperature. The formed core is placed into a plastic injection mold and molded over by a thermoplastic or thermoset material to form the desired shape of the plastic article. The molded plastic article containing the core is submerged in a hot liquid bath to melt and drain the core material from the plastic article.
Many types of devices require specifically configured cavities to support rotating members. Further, the rotating members required supporting features composed of material capable of withstanding specific wear conditions. One example of such a device is an outboard assembly for a motorboat. The outboard assembly transfers power from an interior mounted engine to a propeller positioned within the water. Conventional outboard assemblies are fabricated from an outer housing cast in aluminum. The cast aluminum housing is finish machined to form the required inner mounting structures that support the drive components that drive the propeller. In addition, openings for mounting fasteners and the like are machined into the aluminum casting. The majority of costs associated with the production of an outboard are consumed by the cost of the finish machining operations.
There are several inherent problems associated with the use of aluminum as a material to fabricate an outboard. Although aluminum does not rust as a ferrous metal does in the presence of water, there is a certain amount of material loss associated with the constant immersion in water. Further, cast aluminum is often plagued by porosity that degrades the strength of the casting. Pure aluminum is typically to soft to be used without mixing other strengthening elements, at the sacrifice of corrosion resistance. Typically, bearing races and other surfaces supporting rotating drive components must be fabricated from sufficiently hard materials, thereby requiring inserts to be installed within the aluminum housing.
Accordingly, it is desirable to develop a method of producing a plastic article capable of accommodating rotating members and that substantially reduces finish machining and with economical materials. Further, it is desirable to develop an outboard assembly with economically beneficial materials and processes that is better suited for the water environment.